The present invention relates to a tape reel for use in a magnetic tape cassette such as a digital video cassette (DVC). In particular, the present invention relates to a structure for improving a supersonically welding of a welding boss of a tape reel, a structure for improving the winding shape of a magnetic tape to be wound around a tape reel, a structure for securing the dustproof property of a magnetic tape cassette when not in use as well as preventing the deformation of a lower flange of a tape reel, a structure for preventing a magnetic tape from being damaged due to its contact with a tape reel, and a structure having a characteristic hub.
Also, the invention relates to a magnetic tape take-up device for winding a magnetic tape around a tape reel and, in particular, to a structure for fixing the winding shape of a magnetic tape with the inner surface of an upper flange of a tape reel as a reference.
Generally, in audio equipment and video equipment, there is often used a magnetic tape cassette structured such that a magnetic tape wound around a pair of tape reels is runnably held within a cassette half to thereby execute recording and reproduction.
Referring now to FIG. 20, conventionally, for example, as a magnetic tape cassette which is used as a DVC (digital video cassette), there is known a magnetic tape cassette 130 in which a pair of tape reels 131 with a magnetic tape t wound therearound are rotatably supported within a lower cassette half 133 making a pair with an upper cassette half 132.
On both sides of an opening 134 formed on this side in FIG. 20 of the lower cassette half 133, there are disposed tape guides 135 respectively. The two tape guides 135 respectively guide the magnetic tape t which is fed out from one tape reel 131 and is taken up around the other tape reel 131, and allow the magnetic tape t to pass through a given position in the opening 134.
Also, on the rear side of the lower cassette half 133, there is disposed a reel lock member 139 having a tape reel securing arm 138. The reel lock member 139 is energized by a compression coil spring 140 to bring the tape reel securing arm 138 into engagement with two engaging teeth 141 respectively formed on the outer peripheries of the two tape reels 131, thereby preventing the unprepared rotation of the respective tape reels 131. This can prevent the wound magnetic tape t from loosening.
On the upper cassette half 132, there are mounted an outer lid 150 for covering the opening 134 of the lower cassette half 133, an upper lid 151 and an inner lid 152 in such a manner that they can be freely opened and closed.
On the two side plates 153 of the outer lid 150, there are projectingly provided lock pins 154, respectively. The two lock pins 154 are respectively secured to their associated lid locks 155 which are rotatably disposed on the lower cassette half 133. By the way, reference character 156 designates a lid spring to be mounted on the rotary shaft of the outer lid 150.
The tape reels 131 are respectively structured such that mutually opposing upper and lower flanges 142 and 143 are fixed with a given position relationship between them.
That is, in each tape reel 131, a pivot 147 projectingly provided on a hub 145 of the lower flange 143 is fitted into a pivot hole 146 formed in the central portion 144 of the upper flange 143. Also, a welding boss 148, which is provided on and projected from the hub 145 of the lower flange 143 at a position distant in the radial direction from the pivot 147, is fitted into a welding boss hole 149 formed in the central portion 144 of the upper flange 142 at a position corresponding to the welding boss 148. In this state, in case where a welding horn (not shown) is contacted with the substantially central portion of the leading end face (in FIG. 20, the upper end face) of the welding boss 148, the welding boss 148 can be welded supersonically. As a result of this, the mutually opposed upper and lower flanges 142 and 143 can be fixed with a given position relationship between them.
Now, referring to FIGS. 20 and 21, on the bottom surface 143a of the lower flange 143 that is situated on the opposite side of the hub 145, there is disposed a reference ring 157 which provides a reference for working using a metal mold. The reference ring 157 is present at a position which is more distant in the radial direction than the welding boss 148. The surface 157a of the reference ring 157 is used as a receiving surface for receiving the welding boss 148 when it is welded supersonically, because the surface 157a makes it possible to facilitate the grasping of the dimensional relationship. That is, in case where the surface 157a of the reference ring 157 is contacted with a welding receiving base (not shown) when the welding boss 148 is welded supersonically, the surface 157a allows the welding receiving base to receive pressures applied from the welding horns and vibrations caused by the supersonic oscillation.
In the above-mentioned conventional magnetic tape cassette 130, the surface 157a of the reference ring 157 is used as the receiving surface when the welding boss 148 is supersonically welded. Due to this, the oscillation energy of the supersonic waves from the welding horns is in part lost due to the resonance of the components of the tape reel 131 existing from the welding boss 148 to the reference ring 157, resulting in the low transmission efficiency of the oscillation energy of the supersonic waves from the welding horn to the welding boss 148. In case where the transmission efficiency of the oscillation energy of the supersonic waves is low, it takes time to weld the welding boss 148, which makes it necessary to extend the oscillation time of the supersonic waves, resulting in the poor mass-production aptitude and in the poor welding stability. Further, in case where the welding stability is poor, there is a fear that the mutually opposing attitudes of the upper and lower flanges 142 and 143 can be out of balance, giving rise to the vibratory motion of the surfaces of the tape reel 131 when it is rotated.
It is a first object of the invention to provide a tape reel for use in a magnetic tape cassette which can enhance the transmission efficiency of the oscillation energy of the supersonic waves to the welding boss to thereby be able to shorten the time necessary for supersonic welding of the welding boss as well as to enhance the welding stability.
Next, referring to FIG. 22, the inner surface (lower surface) of the upper flange 142 is formed as a sloping surface 142b which gradually slopes upward from the base end portion (in FIG. 22, the upper end portion a) of the side wall 145b of the hub 145 toward the radial-direction outer side (in FIG. 22, the right side) of the upper flange 142. Also, the inner surface (upper surface) of the lower flange 143 is formed as a sloping surface 143b which gradually slopes downward from the base end portion (in FIG. 22, the lower end portion b) of the side wall 145b of the hub 145 toward the radial-direction outer side (in FIG. 22, the right side) of the lower flange 143.
However, in case where such slopes are formed on the whole areas of the lower surface of the upper flange and the lower surface of the lower flange, it is true that, when the magnetic tape is wound, it can be wound easily; but, there is also a fear that the magnetic tape can be vibrated in the vertical direction.
In case where a given period of time passes after the winding operation of them magnetic tape is started, the rotation speed of the reel drive means and the tape tension become constant, so that the magnetic tape runs stably and thus there is no fear that it can be vibrated in the vertical direction. However, at the beginning of the winding operation of the magnetic tape, the rotation speed of the reel drive means increases gradually and the tape tension also increases, so that the magnetic tape is not be able to run stably.
In this case, since the magnetic tape is vibrated in the vertical direction, the side edges of the wound magnetic tape cannot be superimposed on each other in a well-arranged manner, so that the wound surface of the magnetic tape to be formed by the side edges of the magnetic tape can be out of order and thus it cannot provide a flat surface; that is, there arises a problem that the magnetic tape cannot have a fine winding shape.
Accordingly, it is a second object of the invention to solve the above problem: that is, it is a second object of the invention to provide a magnetic tape reel which allows a magnetic tape to provide a fine winding shape after it is wound.
Next, referring to FIG. 23, on the edge portions of reel holes 133a formed in the inner surface (in FIG. 23, the upper surface) of the lower cassette half 133, there are provided annular-shaped projecting portions 133b, respectively. These annular-shaped projecting portions 133b, when the magnetic tape cassette 130 is not in use (that is, in the state thereof shown in FIG. 23), are respectively contacted with the outer surfaces of the lower flanges 141 of the respective tape reels 131. Due to this, the annular-shaped projecting portions 133b are respectively able not only to prevent entry of dust into the interior of the magnetic tape cassette 130 as much as possible but also to support the weights of the respective tape reels 131 and the weight of the magnetic tape t wound around the respective tape reels 131.
In the above-mentioned magnetic tape cassette 130, in case where the respective tape reels 131 increase in size (outside diameter), when the magnetic tape cassette 130 is not in use, the lower flanges 141 of the respective tape reels 131 are not be able to support the weight of the magnetic tape t, thereby raising a problem that the portions of the lower flanges 141, which are present outside the contact portions of the lower flanges 141 with their associated annular-shaped projecting portions 53b, can be flexed.
In this case, in case where the thicknesses of the lower flanges 141 of the respective tape reels 131 are increased, the above problem can be solved. However, in case where the thicknesses of the lower flanges 141 increase, there arises another problem that there cannot be secured a clearance between the lower flanges 141 and lower cassette half 133 when the magnetic tape cassette 130 is not in use. In case where such clearance cannot be secured, for example, there arises an inconvenience that, due to the vibrations of the magnetic tape cassette half 130 when it is delivered, the lower flanges 141 and lower cassette half 133 are slidingly contacted with each other.
Accordingly, it is a third object of the invention to provide a magnetic tape cassette which can secure a high dust-proof condition in the interior thereof when it is not in use, can positively prevent the lower flanges of the tape reels against deformation, and can secure a sufficient clearance between the lower flanges and a lower cassette half.
Next, referring to FIG. 24, conventionally, as a magnetic tape cassette for a beta cam, for example, there is known a magnetic tape cassette 230 in which a pair of tape reels 231 with a magnetic tape t wound therearound are rotatably supported within a lower cassette half 233 which makes a pair with an upper cassette half 232.
On the two sides of an opening 234 formed on this side in FIG. 24 of the lower cassette half 233, there are disposed tape guides 235 respectively. The tape guides 235 respectively guide the magnetic tape t, which is fed out from one tape reel 231 and is then taken up around the other tape reel 231, and allows the magnetic tape t to pass through a given position in the opening 234. On the other hand, on the upper cassette half 232, there is openably and closably mounted a lid 250 which covers the opening 234 of the lower cassette half 233.
The tape reels 231 are respectively structured such that, with a given clearance formed between the mutually opposed upper and lower flanges 242 and 243, the central portion 244 of the upper flange 242 and the hub 245 of the lower flange 243.
That is, in each of the tape reels 231, a pivot 247 provided on the hub 245 of the lower flange 243 is fitted into a pivot hole 246 formed in the central portion 244 of the upper flange 242. Also, a plurality of welding bosses 248, which are provided on and projected from the hub 245 of the lower flange 243 at positions spaced from the pivot 247 in the radial direction of the hub 245, are respectively fitted into a plurality of welding boss holes 249 formed in the central portion 244 of the upper flange 242 at positions corresponding to the welding bosses 248.
In this state, in case where welding horns (not shown) are respectively contacted with the substantially central portions of the leading end faces of the respective welding bosses 248, the welding bosses 248 can be welded supersonically. As a result of this, the mutually opposed upper and lower flanges 242 and 243 can be fixed with a given clearance between them.
Referring here to FIG. 25, when the lower flange 243 is molded using a metal mold, in the surface 243a (in FIG. 25, the upper surface) of the lower flange 243 that is disposed opposed to the upper flange 242, there are formed a plurality of air discharging recessed portions 251 (in FIG. 24, not shown) which are spaced at given intervals in the peripheral direction of the opposed surface 243a. The respective air discharging recessed portions 251 discharge the air, which enters the interior of the tape reel together with the magnetic tape t when the magnetic tape t is taken up around the tape reel, externally of the tape reel to thereby prevent the magnetic tape t from being wound in disorder.
In the above-mentioned conventional magnetic tape cassette 230 for a beta cam, substantially over the entire periphery of the edge portions 252 of the air discharging recessed portions 251 of the lower flanges 243, there are generated edges 253 when the magnetic tape cassette 230 is molded using a metal mold. This raises a problem that, when the magnetic tape t is taken up around the tape reel, the edges 253 can be contacted with the magnetic tape t, thereby causing the magnetic tape t to be damaged.
This problem, recently, with the enhanced density of the magnetic tape recording, has a seriously ill effect on the recording accuracy and, especially, in a magnetic tape cassette for business such as a beta cam, this problem is serious.
Accordingly, it is a fourth object of the invention to provide a magnetic tape cassette which can prevent a magnetic tape against damage due to its contact with a tape reel to thereby be able to cope with the enhanced density of the magnetic tape recording.
Also, in the case of a tape reel of the above-mentioned type, since the height of the hub thereof is slightly larger than the width of a magnetic tape, while the magnetic tape is being wound around the tape reel, the magnetic tape can be moved up and down when it is moved in the axial direction of the hub, with the result that the magnetic tape wound around the hub of the tape reel can be projected in part in the axial direction of the hub. In order to prevent this, in JP-A-58-187083U, there is disclosed a tape reel structured such that the peripheral surface of the hub thereof is inclined with respect to the axial direction of the hub. Here, FIG. 26(a) is a section view of the tape reel set forth in the above-cited publication, and FIG. 26(b) is a schematic side view of the hub of the present tape reel.
Specifically, in the conventional tape reel shown in FIG. 26, on the upper and lower surfaces of a hub 320, there are disposed upper and lower flanges 322 and 324; the hub 320 and lower flange 324 are formed of resin as an integral body; and, the central portion of the resin-made upper flange 322, which is produced separately from the hub 320, is supersonically welded to the upper end of the hub 320. Although the outer peripheral surface 320a of the hub 320 is circular, the center line A of the circular-shaped outer peripheral surface 320a is inclined by a given angle xcex8 with respect to the axial direction B of the hub 320. Also, the mutually opposed inner surfaces 322a and 324a of the upper and lower flanges 322 and 324 are respectively formed as sloping surfaces which spread out as they go outwardly in the radial direction thereof. The peripheral surfaces of the hub 320 are inclined over the entire areas thereof; and, the peripheral surfaces of the hub 320, which are disposed 180xc2x0 opposed to each other when the hub 320 is viewed from the top plan thereof, are inclined in different directions in the axial direction of the hub 320.
According to the above tape reel, since a magnetic tape 326 to be wound around the hub 320 is contacted with either o f the upper flange 322 or lower flange 324 at each angle of 180xc2x0 when the hub 320 is viewed from the top plan thereof and is thereby restricted in the vertical movement thereof, the magnetic tape 326 can be wound around the hub 320 without being projected in part in the axial direction B of the hub 320.
By the way, generally, the pulling direction of a molding, that is, a molded hub from a metal mold is equal to the axial direction of the hub. However, in the case of the hub 320 shown in FIG. 26 in which the peripheral surfaces of the hub 320 disposed 180xc2x0 opposed to each other when the hub 320 is viewed from the top plan thereof slope in different directions in the axial direction of the hub 320, after it is injection molded, it cannot be pulled out from the metal mold along the axial direction B thereof as it is. For this reason, to manufacture the hub 320, there is necessary a metal mold using a slide core, which not only complicates the structure of a metal mold but also makes it difficult to manufacture the hub 320.
Accordingly, it is a fifth object of the invention to solve the above problem; in particular, to provide a magnetic reel which is easy to manufacture and around which a magnetic tape can be wound with a good winding shape, and a method for manufacturing such tape reel.
Next, as a magnetic tape take-up apparatus, conventionally, in Japanese Patent Unexamined Publication No. Hei.1-217782, there is disclosed a magnetic tape take-up apparatus 440 structured such that, as shown in FIG. 27, a magnetic tape 444 being wound around a tape reel 441 is energized in the direction of a lower flange 442 not in contact with the lower flange 442 by a permanent magnet 443 disposed opposed to the lower flange 442 of the tape reel 441 to thereby arrange the winding shape of the magnetic tape 444 with the inner surface of the lower flange 442 as a reference surface.
The tape reel 441 is mounted on the rotary shaft 446 of a drive mechanism 445 and, in case where the tape reel 441 is driven or rotated by the drive mechanism 445, it takes up the magnetic tape 444 from a tape supply source onto a tape winding surface 447. The permanent magnet 443 is formed in a doughnut shape; and, with the rotary shaft 446 of the drive mechanism 445 loosely fitted into a through hole 448, the permanent magnet 443 is supported through a support portion 449 on a take-up apparatus main body 450.
In the above-mentioned conventional magnetic tape take-up apparatus 440, the permanent magnet 443 is disposed opposed to the lower flange 442 of the tape reel 441 and is used to arrange the winding shape of the magnetic tape 444 with the inner surface of the lower flange 442 as a reference surface.
Therefore, there arises a problem that, when a magnetic tape cassette is set on a recording and reproducing apparatus and the magnetic tape 444 is then made to run, the running passage of the magnetic tape 444, through which it is made to run for the first time by the recording and reproducing apparatus, is shifted from the running passages thereof through which it is made to run for the second time and following times.
That is, for example, in such a recording and reproducing apparatus 460 as shown in FIG. 28, in the first tape running, a magnetic tape 462, which is wound around a tape reel 461 by the conventional magnetic tape take-up apparatus 440, runs through a passage which is shifted to the lower side in FIG. 28 as shown by a two-dot chained line shown in FIG. 28. The reason for this is as follows: that is, since the lower flange of the tape reel 461 has a taper surface sloping downward toward the radial direction of the tape reel 461, the magnetic tape 462 wound around the tape reel 461 is caused to lower downward gradually toward its outer periphery side. In the second and following tape runnings in which the magnetic tape 462 rewound around the tape reel 461 by the magnetic tape take-up apparatus 440 is made to run again, the magnetic tape 462 runs through its normal running passage which is shown by a solid line in FIG. 28. Thus, the running passage of the magnetic tape is shifted between the first tape running and the second and following tape runnings by the recording and reproducing apparatus 460.
Now, description will be given below in detail of the cause of the shifted running passage of the magnetic tape 462.
Firstly, referring to the running passage of the magnetic tape 462 in the magnetic tape take-up apparatus 440, the magnetic tape 462, which is played out from the tape reel 461 of the magnetic tape cassette 463, is guided by tape guides TG0, TG1, TG2 and TG3. This defines the mutually relative positions of the magnetic tape 462 and a recording and reproducing head 464 (cylinder).
In other words, the magnetic tape 462 drawn out from the tape reel 461 is once raised up to its upper limit position by the tape guide TG1 through the tape guide TG0 and the position of the magnetic tape 462 at the upper limit position is controlled by the tape guide TG1; and, after then, the position of the magnetic tape 462 is controlled to its original position between the tape guides TG2 and TG3, and the magnetic tape 462 is then contacted with the recording and reproducing head 464 at a given relative position.
However, in case where the magnetic tape 462 is wound around the tape reel 461 by the conventional magnetic tape take-up apparatus 440, since the lower flange has a taper surface, the play-out position of the magnetic tape 462 from the tape reel 461 is a low position (a position which near to the lower flange 466) shown by a two-dot chained line in FIG. 28.
Due to this, the magnetic tape 462 drawn out from the tape reel 461, as shown by the two-dot chained line in FIG. 28, is not be able to reach the upper limit position to which it ought to be guided by the tape guide TG1; and, therefore, without being controlled in position at the upper limit position by the tape guide TG1, the magnetic tape 462 is controlled in position by the tape guides TG2 and TG3. As a result of this, the running passage of the magnetic tape 462 between the tape guides TG2 and TG3 is shifted from its normal or original running passage. This phenomenon occurs more outstandingly as the magnetic tape 462 wound is present on the outer periphery side.
In case where, as described above, the running passage of the magnetic tape 462 is shifted between the first tape running and the second and following tape runnings by the recording and reproducing apparatus 460, the relative positions of the magnetic tape 462 and recording and reproducing head 464 in the first tape running is different from the relative positions of the magnetic tape 462 and recording and reproducing head 464 in the second and following tape runnings. As a result of this, there arises a problem that, in the recording and reproducing states of the magnetic tape 462, there occurs a serious fault, such as poor interchangeability which cannot be repaired.
Accordingly, it is a sixth object of the invention to provide a magnetic tape take-up apparatus which can arrange the winding shape of a magnetic tape with the upper flange of a tape reel as a reference to thereby be able to stabilize the running of the magnetic tape in a recording and reproducing apparatus.
In attaining the above-mentioned first object, according to a first invention, there is provided a tape reel for use in a magnetic tape cassette, comprising: an upper flange; and, a lower flange disposed opposed to the upper flange and including a hub on the surface thereof opposed to the central portion of the upper flange, wherein a pivot provided on and projected from the hub is fitted into a pivot hole formed in the central portion of the upper flange, a welding boss projectingly disposed at a position of the hub distant from the pivot in the radial direction of the hub is fitted into a welding boss hole formed in the central portion of the upper flange, and, in this state, the welding boss is welded supersonically, whereby the upper and lower flanges are fixed with a given position relationship between them, characterized in that, on the opposite surface of the lower flange to the hub, there are disposed not only a reference ring which is used as a reference for working the tape reel using a metal mold but also, radially inside the reference ring, a receiving surface for use in the supersonic welding of the welding boss.
In the tape reel for use in a magnetic tape cassette according to the first invention, the pivot projectingly provided on the hub formed integral with the lower flange is fitted into the pivot hole formed in the central portion of the upper flange. Also, the welding boss projectingly disposed at a position of the hub distant from the pivot in the radial direction of the hub is fitted into the welding boss hole formed in the central portion of the upper flange. In this state, the welding boss is welded supersonically. Due to this, the upper and lower flanges are fixed with a given position relationship between them.
On the opposite surface of the lower flange to the hub, there is disposed the reference ring which is used as a reference for working the tape reel using a metal mold and, in the portion of the opposite surface of the lower flange to the hub that is situated internally of the reference ring in the radial direction of the tape reel, there is formed the receiving surface for use in the supersonic welding of the welding boss.
In case where the receiving surface, in the supersonic welding of the welding boss, is contacted, for example, with a welding receiving base, the welding boss allows the welding receiving base to receive not only pressures applied from welding horns but also vibrations caused by the oscillation of the supersonic waves. In this case, since the receiving surface is situated in the portion of the opposite surface of the lower flange to the hub that is situated internally of the reference ring in the radial direction of the tape reel, the oscillation energy of the supersonic waves from the welding horns can be prevented from being lost by the resonance of the components disposed from the welding boss to the reference ring.
Also, in attaining the above second object, according to a second invention, there is provided a magnetic tape reel, comprising: a hub for winding a magnetic tape therearound; and, upper and lower flanges respectively positioned on the upper and lower ends of the hub, each of the inner surfaces of the upper and lower flanges being formed so as to slope outwardly in the radial direction of the magnetic tape reel, wherein, on the adjacent portions of the upper and lower flanges to the hub, there are respectively formed flat surfaces lying at right angles to the side surface of the hub and having a given width in the radial direction of the magnetic tape reel.
The radial-direction width of each of the flat surfaces may be preferably larger than the tape winding thickness obtained before, in the tape take-up operation, the motor speed or the tape tensile force becomes constant from the beginning of the tape take-up operation, that is, before the tape take-up ability becomes constant. Specifically, for example, in the case of the above-mentioned DVC, for all sizes of S, M, L, the radial-direction width of the flat surface may be larger than the thickness of a clamp for fixing a tape to the hub, in more specifically, the width may be preferably set in the range of 0.5-5.0 mm.
Also, the clearance between the upper and lower flat surfaces may be set slightly larger than the width of the magnetic tape and may be set as narrowly as possible so long as it does not provide any obstacle to the running of the magnetic tape.
According to the second invention, the portions of the flanges existing in the periphery of the hub do not slope but the flanges are parallel to each other and, in the beginning of the winding operation of the magnetic tape, there is no room for the magnetic tape to move up and down; and, therefore, the winding surface of the magnetic tape consisting of the side edges of the magnetic tape is arranged uniformly, thereby allowing the magnetic tape wound to have a good winding shape.
Also, in attaining the above third object, according to a third invention, there is provided a magnetic tape cassette, comprising: a tape reel including upper and lower flanges, the upper and lower flanges being disposed opposed to each other and fixed with a given position relationship between them; an upper cassette half; and, a lower cassette half disposed opposed to the upper cassette half, the lower cassette half being capable of storing the tape reel in an internal space formed between the upper cassette half and itself, the lower cassette half including a reel hole for insertion and removal of tape reel drive means, wherein the lower flange of the tape reel includes a large-thickness stepped portion formed so as to be continuous with an outside annular-shaped rib, while the portion of the large-thickness stepped portion opposed to the edge portion of the reel hole of the lower cassette half has a thickness set at a given value or more.
Also, in attaining the above third object, according to a fourth invention, there is provided a magnetic tape cassette, comprising: a tape reel including upper and lower flanges, the upper and lower flanges being disposed opposed to each other and fixed with a given position relationship between them; an upper cassette half; and; a lower cassette half disposed opposed to the upper cassette half, the lower cassette half being capable of storing the tape reel in an internal space formed between the upper cassette half and itself, the lower cassette half including a reel hole for insertion and removal of tape reel drive means, wherein, on the edge portion of the reel hole formed in the inner surface of the lower cassette half, there is disposed an annular-shaped projecting portion and, on the radial-direction outside of the annular-shaped projecting portion, there is formed an annular-shaped recessed portion, and, also wherein, in a position which is present in the outer surface of the lower flange of the tape reel and is opposed to the annular-shaped recessed portion, there is disposed an annular-shaped projection to be loosely fitted into the annular-shaped recessed portion.
In the magnetic tape cassette according to the third invention, when the present magnetic tape cassette is not in use, the large-thickness stepped portion formed so as to be continuous with an outside annular-shaped rib, with the portion thereof opposed to the edge portion of the reel hole of the lower cassette half having a thickness set at a given value or more, is contacted with the edge portion of the reel hole of the lower cassette half.
In this state, entry of dust into the interior of the magnetic tape cassette can be prevented and thus a highly dust-proof effect can be secured.
Also, tape reels and a magnetic tape wound around the tape reels are supported on the lower cassette half through the large-thickness stepped portions of the lower flanges of the tape reels with the portions thereof having a thickness set at a given value or more. Not only due to such support of the tape reels through the large-thickness stepped portions of the lower flanges formed continuous with the outside annular-shaped ribs and having a thickness set at a given value or more but also due to the enhanced rigidity of the lower flanges of the tape reels by the portions of the lower flanges having a thickness set at a given value or more, even in a tape reel having a large diameter, deformation of the lower flange of the tape reel due to the weight of the magnetic tape can be prevented positively. Thanks to this, when the magnetic tape cassette is not in use, there can be secured a sufficient clearance between the lower flanges of the tape reels and lower cassette half.
In the magnetic tape cassette according to the fourth invention, when the present magnetic tape cassette is not in use, the annular-shaped projecting portion of the lower half cassette is contacted with the outer surfaces of the lower flanges of the tape reels, and the annular-shaped projections of the lower flanges are loosely fitted into the annular-shaped recessed portion of the lower cassette half and are thereby contacted with the lower cassette half.
In this state, entry of dust into the interior of the magnetic tape cassette can be prevented and thus a highly dust-proof effect can be secured.
Also, tape reels and a magnetic tape wound around the tape reels are supported on the lower cassette half through the annular-shaped projecting portion of the lower cassette half and the annular-shaped projections of the lower flanges. Due to support of the tape reels through the annular-shaped projecting portion of the lower cassette half and the annular-shaped projections of the lower flanges, even in a tape reel having a large diameter, deformation of the lower flange of the tape reel due to the weight of the magnetic tape can be prevented positively. Thanks to this, when the magnetic tape cassette is not in use, there can be secured a sufficient clearance between the lower flanges of the tape reels and lower cassette half.
And, in attaining the above fourth object, according to a fifth invention, there is provided a magnetic tape cassette including a tape reel, the tape reel comprising: an upper flange; and, a lower flange disposed opposed to the upper flange and fixed with a given position relationship with respect to the upper flange, the lower flange including a hub providing a winding surface for winding a magnetic tape therearound, wherein, in the surface of the upper flange that is opposed to the lower flange, or, in the surface of the lower flange that is opposed to the upper flange, there is formed an air discharging recessed portion or an air discharging penetration hole for discharging out the air entering together with a magnetic tape when the magnetic tape is wound around the reel, and, also wherein the edge portions of two sides of the air discharging recessed portion or the air discharging penetration hole in at least radial direction of the flanges are formed into a curve-shape respectively.
In the magnetic tape cassette according to the fifth invention, when the magnetic tape is taken up around the tape reel, the air discharging recessed portion or air discharging penetration hole functions as a flow passage for discharging the accompanying air, thereby being able to prevent the magnetic tape from being wound in disorder. In this case, even when the magnetic tape is contacted with the edge portion of the air discharging recessed portion of the tape reel, the required curved shape applied to the edge portion can prevent the magnetic tape against damage.
Also, in attaining the above fifth object, according to a sixth invention, there is provided a magnetic tape reel, wherein the outer surface of a clamp member for holding a leader tape between itself and a recessed portion formed in a hub for winding a magnetic tape therearound and the peripheral surface of the hub that, when viewed from the top plan surface of the hub, is disposed 180xc2x0 opposed to the recessed portion are respectively taper surfaces which slope in mutually different directions in the axial direction of the magnetic tape reel.
Further, in attaining the above fifth object, according to a seventh invention, there is provided a method for manufacturing a magnetic tape reel having a structure that, in a hub for winding a magnetic tape therearound, there is formed a recessed portion for holding a leader tape using a clamp member, and the peripheral surface of the hub that, when viewed from the top plan surface of the hub, is disposed 180xc2x0 opposed to the recessed portion is a taper surface sloping toward the axial direction of the hub, the method comprising the steps of: injection molding the magnetic tape reel; and, pulling out the injection molded magnetic tape reel along the axial direction thereof.
According to the sixth and seventh inventions, the hub includes the sloping peripheral surface only on one side thereof and the recessed portion of the hub, which is formed on the opposite side of the sloping peripheral surface and into which the clamp member can be fitted, does not have any gradient. Therefore, after the magnetic tape reel is molded, the hub, as it is, can be pulled out along the axial direction of the magnetic tape reel. This does not require a complicated metal mold using a slide core and thus the hub can be manufactured easily using a metal mold having a simple structure.
Also, in the case of the clamp member, there is formed a sloping surface on the peripheral surface thereof but, after it is injection molded, it can be pulled out along the axial direction thereof as it is. Therefore, also when manufacturing the clamp member, there is not required a complicated metal mold using a slide core and thus the clamp member can be manufactured easily using a metal mold having a simple structure.
Further, in attaining the above sixth object, according to an eighth invention, there is provided a magnetic tape take-up apparatus, comprising: drive means for rotating a tape reel to thereby wind a magnetic tape around the tape reel at a winding speed of 2-2.5 m/s and with a winding tension of 60-70 g; and, magnetic field generating means including a magnet formed of neodymium and having a magnetic flux density of 12800-13300 G, and disposed opposed to the upper flange of the tape reel with a clearance of 12-17 mm between them for applying a magnetic field to the magnetic tape from the upper flange side of the tape reel.
The area of the portion of the magnetic field generating means opposed to the upper flange of the tape reel may be preferably 1.3 times or more the area of the side surface side of the magnetic tape to be wound around the tape reel.
In the magnetic tape take-up apparatus according to the eighth invention, the drive means rotates the tape reel to thereby wind a magnetic tape from a tape supply source around the tape reel at a winding speed of 2-2.5 m/s and with a winding tension of 60-70 g. Also, the magnetic field generating means including a magnet formed of neodymium and having a magnetic flux density of 12800-13300 G applies a magnetic field to the magnetic tape from a position where it is opposed to the upper flange of the tape reel with a clearance of 12-17 mm between them. Due to this, the magnetic field given by the magnetic field generating means can be applied uniformly to the magnetic tape from the upper flange side of the tape reel.
In the magnetic tape take-up apparatus according to the eighth invention, the area of the portion of the magnetic field generating means opposed to the upper flange of the tape reel, preferably, may be set 1.3 times or more the area of the side surface side of the magnetic tape to be wound around the tape reel.